Photoelastic study of dense granular free-surface flows

Area of Science:

• Physics of granular materials
• Fluid dynamics
• Rheology

Background:

• Granular flows exhibit complex behaviors transitioning between solid-like and fluid-like regimes.
• Understanding force transmission is crucial for modeling granular avalanches.

Purpose of the Study:

• To investigate the distribution of dynamic forces within granular free-surface flows.
• To quantify stress tensor components and their evolution in avalanches.
• To compare discrete granular flow behavior with continuous fluid models.

Main Methods:

• Experiments using photoelastic disks released from an incline to create 2D avalanches.
• Particle tracking to measure density and velocity profiles.
• Photoelastic technique to visualize and quantify inter-particle forces.

Main Results:

• Coarse-grained stress tensor profiles show hydrostatic pressure increase with depth.
• Force chains preferentially align with gravity and shear forces.
• The stress tensor behavior in granular flows is analogous to continuous fluid flow.

Conclusions:

• Discrete granular flows exhibit behaviors comparable to continuous fluid dynamics.
• The study provides insights into the role of inter-particle forces in avalanche dynamics.
• Findings support analogies between discrete and continuous flow models.